1. Field of the Invention
This invention relates to the field of explosive compositions, especially compositions useful for thermobaric weapons, and further relates to thermobaric weapons and methods for making and employing the same.
2. Description of the Related Art
Standard-type explosives selected for fragmentation and/or penetration effects constitute one of the most commonly used categories of conventional explosives. Such standard explosives typically comprise a relatively high density, oxygen-balanced composition. An example of a weapon containing such standard explosives is the shoulder-launched rocket, which is useful, for example, in repelling and destroying armored vehicles and the like. The shaped charge of the shoulder-launched rockets creates a high velocity metal jet that inflicts damage over a relatively narrow radius. As a result, conventional fragmentation/penetration weapons are primarily useful against confined and discrete targets located directly along the travel path of the weapon. Standard explosives are less effective against expansive targets, such as multi-room buildings, and hidden or entrenched targets (e.g., field fortifications, machine gun posts, and the like) that are not in a direct path or cannot be reached by a direct path of penetration.
Volumetric explosives constitute another explosive weaponry category, and are designed to overcome shortcomings of standard explosives. Volumetric explosives are generally characterized by their superb incendiary and blast effects. For example, some volumetric explosives are capable of creating large fireballs upon detonation. Fuel-air explosives (FAEs) fall within this category. Generally, FAEs are aerobic fuel-rich gels or slurries and are aerobic, i.e., compositions containing a fuel component that combusts with oxygen in the surrounding atmosphere upon detonation. FAE weapons generally contain a “burster” that, upon detonation, disperses the fuel component outward as an aerosol and then either detonates or ignites to promote the aerobic reaction of the fuel component with the oxygen in air. The relatively low-order burning event generated by the burster limits the extent of damage imparted by the FAE. For example, the FAE usually have limited success in reaching deeply burrowed targets.
A class of explosives known as thermobaric explosives (TBX) also falls within the volumetric weaponry category. Thermobaric explosives are designed to produce heat and pressure effects instead of armor piercing or fragmentation damage effects. Thermobaric explosives are generally fuel-rich compositions containing a nitramine, characterized by the energy release occurring over a longer period of time than standard explosives, thereby creating a long-duration pressure pulse. Without wishing to be bound by a particular theory, it is believed that the thermobaric explosive undergoes the following stages upon detonation. In a first stage, an initial shock (or blast) wave from the explosive causes the nitramine to undergo anaerobic detonation in an essentially reduction-oxidization (redox) reaction occurring within hundreds of microseconds to disperse the fuel particles. In a second stage, the anaerobic combustion of fuel particles occurs within hundreds of microseconds. The anaerobic combustion process occurs along the detonation shock wave and consumes fuel particles in close proximity to the detonating nitramine. In the third stage, the fuel-rich energetic material is subject to aerobic combustion, which results from the shock wave mixing with oxygen in the surrounding air and has a duration of, for example, several microseconds. Residual nitramine is preferably present in the shock wave and undergoes anaerobic reaction with the fuel particles to propagate the shock wave and increase dispersion of the fuel particles.
Thermobaric explosives typically are plastic bonded explosive (PBX) compositions, which typically comprise a metallic fuel and an oxidizer or nitramine. One drawback associated with the use of a PBX composition in a thermobaric weapon is that the metallic fuel sometimes does not combust completely. Due to the diminished return of increasing fuel content, the fuel content is regulated so as to not exceed 35 weight percent, and more typically falls within a range of 20 to 35 weight percent. Due to this low fuel content, most successful traditional thermobaric weapons have been designed relatively large in size to furnish adequate fuel. Weight and size penalties accompany the large size and weight of such weapons. Although decreasing the size of the weapon can overcome this drawback, smaller thermobaric weapons tend to generate insufficient overpressure to kill targets “in the open.”
Without wishing to be bound by any theory, it is also believed by the present inventors that TBX compositions generally act like “high” or “underwater” explosives and, as such, are characterized by shock-propagated reactions. Shock propagated reactions can bounce off of walls and succumb to rarefaction in closed spaces. Although shock wave rarefaction enables a high degree of mixing and multiple reactions, it also can limit the effective range of the thermobaric explosive, especially in closed or labyrinth-like spaces such as caves or multi-room buildings.
3. Objects of the Invention
It is one object of this invention to provide a pressable explosive composition especially suited for use in thermobaric weapons.
It is another object of the invention to provide a pressed thermobaric explosive, especially one capable of penetrating deeply into complex and entrenched structures, such as caves and multi-room buildings.
It is a further object of the invention to provide a pressed thermobaric explosive less prone to adverse performance caused by rarefaction in enclosed spaces.
It is another object of the invention to provide a pressed thermobaric explosive having improved sensitivity characteristics, including electrostatic and frictional sensitivities.
It is another object of this invention to provide articles of manufacture, such as but not necessarily limited to warheads, projectiles, grenades and munitions comprising the pressed thermobaric explosive of this invention.
It is yet another object of this invention to provide methods for making the pressable explosive compositions, thermobaric explosives, and articles of manufacture of the present invention.